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Microstructure and Magnetic Properties of (Nd, Pr)_(10.5)(Fe,Zr)_ ( 83.5-x)Co_xB_6 Alloys

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Journal of Rare Earths 2005年第S1期23卷 274-276页

作者：刘锦云王克强查五生 College of Material Science & Engineering Xihua University Chengdu 610039 China

Effects of addition of Co on the microstructure and magnetic properties of the series of (Nd, Pr)_ 10.5(Fe, Zr)_ 83.5-xCo_xB_6 alloys, which were prepared by over-quenching and post annealing method, were investigated. The free surface microstructures of crystallized ribbons were observed by means of Atom force microscopy (AFM). The significant improvement of remanence B_r and maximum energy product (BH)_m by Co addition is attributed to the increase of each phase magnetization and the exchange-coupling regions between the soft and hard magnetic phases. However, Co addition decreases the intrinsic coercivity (H_ ci), resulting from the grain coarsening and the (Nd,Pr)_2Co_ 14B phase, which has less anisotropy field (HA) at room temperature. The value of 2%(atom fraction) of Co addition is optimal. The bonded magnets of (Nd,Pr)_ 10.5(Fe,Zr)_ 81.5Co_2B_6 has the best combination of properties, which are B_r=0.662 T, H_ ci=616 kA·m -1 and (BH)_ max=74.0 kJ·m -3.

关键词： metal materials Co melt-spun magnets magnetic properties microstructure rare earths

Large Magnetic Entropy Effect in La_(2/3)Ca_(1/3)MnO_3

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Journal of Rare Earths 2004年第2期22卷 232-234页

作者：彭振生 Department of Physics Suzhou Advanced Normal College Suzhou 234000 China

The magnetocaloric effect in the colossal magnetoresistance material La_(2/3)Ca_(1/3)MnO_3 was studied. From the measurements of temperature dependence of magnetization in various magnetic fields, the large magnetic entropy change associated with the ferromagnetic-paramagnetic transition was discovered. This result suggests that perovskite manganites are suitable candidates as working substance in magnetic refrigeration technology.

关键词： metal materials magnetocaloric effect colossal magnetoresistance perovskite entropy rare earths

Studies on Oxygen Characteristics of YBa_2Cu_3O_(7-x) and Its Applications to Air Separation and Gas Purification

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Journal of Rare Earths 2005年第1期23卷 112-115页

作者：杨德林莫炯卢红霞郭益群高之爽胡行 School of Physical Engineering and Key Laboratory of Material Physics of Ministry of Education of China Zhengzhou University Zhengzhou 450052 China Department of Chemistry Zhengzhou University Zhengzhou 450052 China

Oxygen diffusion and oxygen selective adsorption properties of rare earths material YBa_2Cu_3O_(7-x) (YBCO) were investigated by thermogravimetric, oxygen static adsorption and selectivity adsorption experiments. The results show that YBCO is a very good deoxidizing material. The oxygen desorption of YBCO begins remarkably at about 400 ℃, mass loss can arrive at 1.2% of its original quantity at 800 ℃. Oxygen can be completely absorbed back into the sample again when temperature descends to 400 ℃. The oxygen adsorption selectivity, reproducibility and oxygen adsorption under very low oxygen partial pressure make the material desirable for air separation and gas purification. High purity nitrogen gas was produced with the YBCO molecular sieves in the air separation and gas purification experiments. 0.017 m^3 of high purity nitrogen (>99.9999%) can be obtained with 1 kg YBCO molecular sieve in one cycle. As a deoxidant, an obvious advantage of YBCO is that no hydrogen is needed in its applications.

关键词： metal materials YBCO oxygen characters gas separation and purification rare earths

Dependence of Effective Anisotropy on Grain Size in Nanocrystalline Nd_2Fe_(14)B Hard Magnetic Material

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Journal of Rare Earths 2005年第1期23卷 52-54页

作者：冯维存高汝伟韩广兵朱明刚李卫孙光飞 SchoolofPhysicsandMicroelectronics ShandongUniversityJinan250010China DivisionofFunctionalmaterials CentralIronandSteelResearchInstituteBeijing100081 China SchoolofmaterialsScience UniversityofScienceandTechnologyBeijingBeijing100083China

Taking nanocrystalline Nd_2Fe_(14)B as a typical sample, based on Herzer′s random anisotropy theory and the cubic grain model, the partial exchange-coupling interaction model was established and the dependence of effective anisotropy constant K_(eff) on grain size was investigated. Calculation results reveal that the exchange-coupling interaction enhances and the effective anisotropy of material K_(eff) decreases with the reduction of grain size. The variation of K_(eff) is basically the same as that of coercivity. The decrease of effective anisotropy is the main reason of the reduction of coercivity for nanocrystalline Nd_2Fe_(14)B permanent magnetic material.

关键词： metal materials effective anisotropy grain size exchange-coupling interaction coercivity rare earths

Kinetics of Formation of Large-Dimension Rare Earth Inclusion in Steels

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Journal of Rare Earths 2004年第3期22卷 403-405页

作者：赵晓栋姜江李国宝李风照 School of Material Science and Engineering Shandong University Jinan 250061 China Jinan Iron & Steel Group Corporation Jinan 250101 China

The elemental distribution within the large-dimension rare earth inclusion in steels was studied through analysis on plane distribution of elements by EPMA (Electron Probe Microanalyzer). The kinetics and mechanism of formation of RE inclusion were discussed, taking 5CrNiMo steel with the addition of RE and other microalloying elements as example. RE inclusions nucleate on oxides and sulphides with high melting point and grow up separately, then integrated by relatively high surface activity, which is a particular characteristic of RE elements, in liquid phase and during the course of solidification. Finally, the fine and dispersed RE inclusions merge and grow into a large-dimension one.

关键词： metal materials RE inclusion large-dimension nucleate separately-merge and grow kinetics rare earths

Effect of Rare Earths on Properties of BNbRE Rail Steel

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Journal of Rare Earths 2003年第4期21卷 469-473页

作者：李春龙智建国王荣 Baotou Iron & Steel(Group)Corporation

The development and properties of BNbRE rail steel and the effect of RE on rail steel were studied. The results show that the properties of rail steel ( σ b≥980 MPa, δ 5≥8%) can be improved by adding RE and niobium and adjusting the content of C, Si and Mn in steel. At the same time, the abrasion resistance, contact fatigue and fatigue property of BNbRE rail steel are excellent. It also shows that RE in rail steel has the functions of purifying steel, modifying inclusion and micro alloy action effect. The improved steel making process enhances the quality of molten steel. Although the content of RE is low, excellent properties of BNbRE rail steel are achieved.

关键词： metal materials rail steel property rare earths

Effect of Zr on Microstructure and Magnetic Properties of Nanocrystalline (Nd, Pr)FeB/α-Fe Composite Alloys

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Journal of Rare Earths 2004年第S1期22卷 108-111页

作者：刘锦云刘颖王克强查五生涂铭旌 College of Material Science & Engineering Xihua University Chengdu 610039 China College of (Material) Science & Engineering Sichuan University Chengdu 610065 China

For nanophase (Nd, Pr)FeB/α-Fe composite alloys were prepared by melt spinning, the appreciable addition of Zr reduces their average grain size. Observed by atom force microscopy (AFM), the average grain diameter of crystallized ribbons on their free surface, reduces from 175 nm of Zr-free alloy to 79 nm of Zr-1at%, by about 55%. If the concentration exceeds 1%, the effects of Zr on fining grain size are evidently weakened. The average grain size on free surface of Zr-1.5at% is 72 nm. With the addition of 1at% Zn, the bonded magnets has the best combination of properties: B_r=0.675 T, H_(ci)=616 kA·m^(-1), (BH)_(max)=77 kJ·m^(-3). Below 1at%, the coarser grains lead to a lower magnetic property. Beyond 1at%, the layer of Zr-rich intergranular phase will thicken, which results in weakening of the exchange coupling among adjacent grains, and then causes degrading of magnetic properties of magnets.

关键词： metal materials Pr-based permanent magnets nanocrystalline composite Zr dopant melt spining (microstructure ) magnetic properties rare earths

Study on Y-Base Rare Earth Alloy in Ultra-High Hardfacing

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Journal of Rare Earths 2003年第3期21卷 384-386页

作者：王宝森李午申冯灵芝张亚梅 School of materials Science & Engineering Tianjin University

The effect of Y base rare earth alloy in ultra high hardfacing was observed by means of OM, SEM and XRD. Precipitated carbide can be metamorphosed and spheroidized in surfacing by adding Y base rare earth alloy, which contributes to the increase of precipitated carbide. Rare earth combined with oxygen and sulfur can improve the morphology of slag inclusion as well as purify surfacing. The result shows proper rare earth alloy in surfacing can fine its microstructure, improve hardness and impact toughness.

关键词： metal materials surfacing precipitated carbide rare earths alloy

Preparation of Rapidly Quenching (Nd,Pr)_(12)(FeCoZr)_(82)B_6 Alloy and Magnetic Properties of Bonded Magnets

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Journal of Rare Earths 2004年第4期22卷 497-500页

作者：查五生刘颖高升吉涂铭旌 College of Material Science & Engineering Sichuan University Chengdu 610065 China College of (Material) Science & Engineering Xihua University Chengdu 610039 China

The optimum quenching rates and annealing conditions to prepare near stoichiometrical (Nd,Pr)(12)(FeCoZr)(82)B-6 bonded magnets were investigated by using sub-overquenching and post annealing method. The quenching rates, annealing temperatures, and annealing time directly influence the microstructure and magnetic properties of alloy ribbons. The optimum magnetic properties of bonded magnets are achieved by melt spinning at 24 m (.) s(-1) wheel surface speed, annealing at 655 degreesC for 10 min, and bonding with 3.25% (mass fraction) epoxy. The best magnetic properties of remanence B-r, intrinsic coercivity H-ci and maximum energy product (BH)(max) are 0.669 T, 811 kA (.) m(-1), and 75 kJ (.) m(-3), respectively.

关键词： metal materials permanent magnet Pr-based bonded magnets melt spinning magnetic properties rare earths